1. Field of the Invention
The present invention relates to a method for joining two strips each including a laminate of a release liner and a pressure-sensitive adhesive layer. It relates also to the structure of a joined portion (joint) formed by the method, and to a continuous strip composed of two or more strips joined by the method.
2. Description of the Related Art
Strips each including a pressure-sensitive adhesive layer and a release liner (such as pressure-sensitive adhesive tapes) are used in a variety of fields (typically see Japanese Unexamined Patent Application Publication (JP-A) No. 2007-217553 corresponding to US20070190280A). During manufacture of strips, the strips are joined with each other typically when a failed portion, if occurring, is removed and the residual portions are joined to give a product, or when short-length strips are joined to give a long (continuous) product.
Of these strips, pressure-sensitive adhesive tapes each having a pressure-sensitive adhesive layer composed of an acrylic foam and thereby being thick have been joined by a method in FIG. 4. In this method, an end cross-section of one pressure-sensitive adhesive tape is butted against an end cross-section of the other pressure-sensitive adhesive tape to thereby bond the two pressure-sensitive adhesive layers (2a and 2b) with each other, and two release liners (1a and 1b) are affixed through a pressure-sensitive adhesive tape (hereinafter also referred to as a “joint tape”).
The resulting continuous strip (pressure-sensitive adhesive tape) composed of strips joined by the above method, however, suffers from problems when the release liners are removed from the pressure-sensitive adhesive tape upon use. More specifically, with reference to FIG. 5, there is an edge 10 (release edge) of one release liner at the joint portion, and the peel force locally increases at the edge portion to cause “binding (catch or hang-up)”. Thus, the peeling workability is insufficient, or the release liner breaks to reduce the productivity. Additionally, there occur problems in product quality. Typically, the increased peel force at the edge portion causes a crevice in the joint between the pressure-sensitive adhesive layers, and sealing at the joint portion becomes insufficient.